Socket Selection

TiOS supports up to 16 sockets, but there may be platforms with less than 16 sockets available. You can obtain the number of sockets available for your platform using the sock.numofsock read-only property.

Since there can be multiple sockets, you must state to which socket you are referring when changing properties or invoking methods. This is done using the sock.num property. For example:

Tibbo BASIC

							sock.protocol = 1

Can you tell to what socket the statement above applies? Neither can the platform. Thus, the correct syntax would be:

Tibbo BASIC

							sock.num = 0
							sock.protocol = 1
						

Now the platform knows with which socket you're working. Once you have set the socket selector (using sock.num), every socket-specific method and property after that point is taken to refer to that socket. Thus:

Tibbo BASIC

							sock.num = 0
							sock.protocol = 1
							sock.connectiontimeout = 10
							sock.httpmode = 1 ' etc
						

The events for this object are not separate for each socket. An event such as on_sock_data_arrival serves all sockets on your platform. Thus, when an event handler for the socket object is entered, the socket selector is automatically switched to the socket number on which the event occurred:

Tibbo BASIC

							sub on_sock_data_arrival
								dim s as string
								s = sock.getdata(255) ' Note that you did not have to specify any sock.num preceding this statement.
							end sub
						

As a result of this automatic switching, when an event handler for a socket event terminates, the sock.num property retains its new value (nothing changes it back). You must take this into account when processing other event handlers that make use of a socket (and are not socket events). In other words, you should explicitly set the sock.num property whenever entering such an event handler, because the property might have been automatically changed prior to this event. To illustrate:

Tibbo BASIC

							sub on_sys_init ' This is always the first event executed.
								sock.num = 0  ' Supposedly, this would make all subsequent properties and methods refer to this socket.
							end sub
							 
							sub on_sock_data_arrival ' Then, supposing this event executes.
								dim s as string
								s = sock.getdata(255) ' However, this event happens on the second socket. So now sock.num = 1.
							end sub
							 
							sub on_ser_data_arrival ' And then this serial port event executes.
								sock.txclear ' You meant to do this for sock.num = 0 (as specified at on_sys_init). But now sock.num was changed to 1! Oops...
							end sub
						

To recap, only one of two things may change the current sock.num: (1) manual change or (2) a socket event. You cannot assume the number has remained unchanged if you set it somewhere else (because a socket event might have happened since).